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Electronics => Electronics => Topic started by: aruna1 on October 31, 2010, 07:33:44 AM

Title: 433MHz or 315MHz rf?
Post by: aruna1 on October 31, 2010, 07:33:44 AM: hi
following are two rf transmitteres.they are same price but one is 433MHz and other is 315MHz.

http://www.sparkfun.com/commerce/product_info.php?products_id=8946 (http://www.sparkfun.com/commerce/product_info.php?products_id=8946)
http://www.sparkfun.com/commerce/product_info.php?products_id=8945 (http://www.sparkfun.com/commerce/product_info.php?products_id=8945)

what are the difference between this two except frequency?
and which module should I buy?
thanks
Title: Re: 433MHz or 315MHz rf?
Post by: waltr on October 31, 2010, 09:05:15 AM: There is not much difference in performance between the two RF modules. Pick the one that uses a frequency that is legal in your country.
Title: Re: 433MHz or 315MHz rf?
Post by: aruna1 on October 31, 2010, 12:22:31 PM: oh i see thank you very much for the info
anyway is there any advantage of one frequency over other if we dont have any legal problem about frequency?
Title: Re: 433MHz or 315MHz rf?
Post by: TrickyNekro on November 03, 2010, 04:00:59 AM: They do have a different wave length and that says a lot...

The 433MHz one should behave better on narrow environments, so if your application stays inside then it's better to have that module... On the other hand 315MHz have a longer wavelength and you will get a little bit more range outdoors in an open environment...

Keep in mind that this modules may not have encryption which is vital...
Manchester encryption is an option and quit easy to utilize...

Also the antenna should be different in case you make it and don't buy a pre-made...
λ/4 straight antenna is a good one.... where λ is the wavelength...
λ/2 straight antenna is an option too... but it gets rather long...

To calculate the antenna length the formula is

c = λ*f

Where: c is the speed of light in vacuum space and proximately in the air medium
λ is the wavelength
f is the frequency of the wave hence the frequency of your transmitter

That's it for now... If you want something else... FIRST Google it, then ask ;-)
Title: Re: 433MHz or 315MHz rf?
Post by: chelmi on November 03, 2010, 09:08:38 AM: Quote from: TrickyNekro on November 03, 2010, 04:00:59 AM
Keep in mind that this modules may not have encryption which is vital...
Manchester encryption is an option and quit easy to utilize...

Encoding, not encryption.
Title: Re: 433MHz or 315MHz rf?
Post by: aruna1 on November 03, 2010, 10:17:00 AM: @ TrickyNekro & chelmi

thank you, :)
I have already ordered a 315MHz one
Title: Re: 433MHz or 315MHz rf?
Post by: TrickyNekro on November 04, 2010, 03:17:01 AM: Quote from: chelmi on November 03, 2010, 09:08:38 AM
Quote from: TrickyNekro on November 03, 2010, 04:00:59 AM
Keep in mind that this modules may not have encryption which is vital...
Manchester encryption is an option and quit easy to utilize...

Encoding, not encryption.

Details.... :P
Title: Re: 433MHz or 315MHz rf?
Post by: waltr on November 04, 2010, 07:04:58 AM: Google "Manchester Encoding".
Title: Re: 433MHz or 315MHz rf?
Post by: blackbeard on November 04, 2010, 12:30:49 PM: they are not too different. the real advantage is being able to send 2 way data by having a transmitter at 1 frequency and a receiver on the other.